1. The problem statement, all variables and given/known data Hi! I need help with a problem regarding the corotational speed en energies for oxygen ions around Jupiter. I'm stuck 2. Relevant equations See below 3. The attempt at a solution I know that the maximum magnetospheric plasma density is about 1000-50000 cm^-3. I also know that the formula for the circumference of Jupiter (or any other planet if I'm correct) is: 2*pi*L*Rj. The L values should be between 1-10. The critical velocity has a formula and it is: (v_crit)^2=Omega_gyro*Omega_rotation*Rj^2*L^2 and I believe that I need to use this. In that case, I need to know how to calculate Omega_gyro and Omega_rotation (which are the rotational frequencies). What should I do? When it comes to the energy, I believe that I can use E=mv^2/2 , where m is the mass of the ion. Correct? Thanks!